Given its essential role in the repair of DSBs, the germline missense mutations in genes encoding the MRN complex cause human genomic instability syndromes such as: Ataxia-Telangiectasia-like disorder (ATLD, mutations in MRE11), Nijmegen breakage syndrome-like disorder (NBSLD, mutations in RAD50), and Nijmegen breakage syndrome (NBS, mutations in NBS1), respectively [11]. The gene discussed is RAD50; the disease is Nijmegen breakage syndrome.